Abstract
The article investigates the thermal behaviour of a solar collector retrofitted with a natural draught unit. The objective of this work is to draw a comparative line between a system that is equipped with a circular vertical channel and the conventional one. The effectiveness of the solar heating system and how to further improve the prevailing system are examined in this study. The flat plate solar collector was used to assess the dynamics of the system. The Hottel–Whillier–Bliss equation was used to obtain the useful heat gain rate. The instantaneous collector efficiency was reduced by 22.84%. The net heat loss encountered with natural draught was augmented by 10.89%. The net pressure drop along the length of the collector was increased when a solar collector related to the circular chimney. The stagnant temperature of the collector with the natural draught was decreased by 3.20%. The heat loss to the surrounding was computed to be 33.94% of the net energy received by a solar collector connected with the circular stack. The Fanning friction factor for airflow was reduced in the system equipped with natural draught. The static pressure was marginally dropped at the inlet, whereas it was steeply increased at the outlet of the solar collector. The static pressure would be the same for both systems at collector length l = 0.84 m. The inference can be deducted from the comparative analysis that the air stream flow behind the collector plate and could provide better prospects for a collector unit equipped with natural draught at the exhaust end of the solar dryer.
Highlights
The scarcity of conventional resources and the inadequacy of available thermal units are some of the factors which encourage researchers to focus on the application of solar energy in thermal systems
Selective coating of absorber plate was performed to increase the thermal performance of the solar air heaters [14], by using porous/nonporous beds to enhance thermal storage [15,16], or by introducing
The comparative assessment of the natural draught system with the conventional type of dryer was based on heat analysis and temperature and pressure distribution along the length of the collector
Summary
The scarcity of conventional resources and the inadequacy of available thermal units are some of the factors which encourage researchers to focus on the application of solar energy in thermal systems One such system is the drying of perishable food items. The mode of heating was bit revolutionised, and the natural circulation of air used to be incited by a blower (forced circulation) The problem with this system was that the temperature of the product was not controlled, and it was replaced by an indirect type of active device. Cabinet-type dryers are mainly used for drying timber, whereas indirect dryers are used for food grains, tea, spices etc Another aspect of drying system is the solar collector that provides the conditioned air to the drying chamber
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